Formation and Reactivity of the Radical Cation of Bromobenzene in Aqueous Solution: A Pulse Radiolysis Study

Article abstract of DOI:10.1021/j100017a036

A transient optical absorption band (λ_max=325 nm) is formed upon reaction of ^. OH radical with bromobenzene in neutral aqueous solution and is assigned to the OH adduct.In strongly acidic solution (HClO4 > 3 mol dm³), the OH adduct undergoes H⁺-catalyzed dehydroxylation to form the bromobenzene radical cation.This radical cation absorbs at 550 nm and at 270-310 nm.Even at this high H+ concentration, only a fraction of the OH adduct is converted to the radical cation.SO4^.- reacts with bromobenzene to form the hydroxycyclohexadienyl radical (λ_max=325 nm) and the phenoxyl radical (λ_max=400 nm).The bromobenzene radical cation is also observed in irradiated 1,2-dichloroethane solutions.C6H5Br^.+ is a strong one-electron oxidant and oxidizes Br-, SCN-, and organic sulfides with high rate constants.C6H5Br^.+ undergoes electron transfer reaction with Cl- to establish an equilibrium, from which a reduction potential value for C6H5Br^.+/C6H5Br was determined to be 2.31+/-0.15 V versus NHE.